a(n) = position of 5 + n^2 in A004432.

Terms

a(0) =1a(1) =2a(2) =5a(3) =8a(4) =15a(5) =22a(6) =31a(7) =40a(8) =55a(9) =69a(10) =87a(11) =104a(12) =126a(13) =149a(14) =172a(15) =198a(16) =228a(17) =256a(18) =288a(19) =323a(20) =357a(21) =394a(22) =433a(23) =473a(24) =514a(25) =557a(26) =603a(27) =651a(28) =700a(29) =751